Traffic regulations relating to lane changing include, for example, “no passing”, “no passing on the right for overtaking” (see FIG. 1), and “no lane changing”.
The traffic regulation of “no passing” is very often set in a section of one lane on each side of two-way traffic, when there is a predetermined volume of traffic, or when visibility is poor due to, for example, a curved road.
Similarly, the traffic regulation of “no lane changing” is very often set particularly when lane changing is expected to entail hazards, such as “a place near a corner of a road”, “a place near the top of an uphill”, “a steep slope”, “a sag”, and “a tunnel”.
Patent Document 1 may be referred to as a document that discloses a technique relating to the present invention.
Similar traffic regulations are adopted also in a number of foreign countries (FIG. 6). FIGS. 6(A), 6(B), and 6(C) show signs representing no passing in the U.S., France, and the UK, respectively. FIGS. 6(D) and 6(E) show signs representing no passing in Germany.    Patent Document 1: Japanese Patent Application Publication No. JP-A-7-63567